A major focus of research and development efforts in the pharmaceutical industry is on the formulation of acceptable oral pharmaceutical compositions. More particularly, these efforts are concentrated on making oral pharmaceuticals that are palatable to the consumer. Chief among the concerns of pharmaceutical manufacturers in this area is the development of drugs that are as palatable as they are efficacious. The importance of these research efforts is greatest where the pharmaceuticals at issue are intended to ameliorate a patient's medical condition or alleviate their symptoms in cases of terminal illness. Renal diseases, such as chronic renal failure, are examples of such illnesses.
In cases of chronic renal failure, hyperphosphatemia, or excess phosphorus retention, plays a major role in the development of secondary hyperparathyroidism and osteodystrophy. Antacids or prescription medications are commonly used to manage or prevent hyperphosphatemia by binding dietary phosphorus and, thus, preventing its absorption into the gastrointestinal tract.
Phosphorous binders bind phosphorus in the form of a phosphorous ion within the stomach and intestines. This process is thought to result from a chemical reaction between dietary phosphorus and the cation present in the binder compound. The reaction causes the formation of insoluble and hence unabsorbable phosphate compounds. The cation in some phosphorous binders is aluminum or calcium. Despite their capacity for binding phosphorus, large quantities of antacids must be ingested over a long period of time for them to be effective. Therefore, dosage size and palatability are particularly important for patients with chronic renal disease.
Prescription medications typically effective in managing or preventing hyperphosphatemia include calcium acetate. Calcium acetate treatment is one of the most effective methods for management of chronic renal disease. When administered orally, calcium acetate is more effective than any other calcium-containing binder in binding phosphorus. Used alone or in combination with other materials, calcium acetate binds phosphorus in the gastrointestinal tract and reduces the percentage of consumed phosphorus (i.e., of a given “dose” of phosphorus) which is absorbed into the bloodstream. This compound is most effective in reducing phosphorous absorption when it is administered close in time to food consumption. Despite these benefits, calcium acetate treatments heretofore known in the art have not been without their drawbacks.
Calcium acetate is a solid, and to date, it is formulated in various solid dosage forms, such as pills and tablets. See, e.g., U.S. Pat. Nos. 6,875,445, 4,870,105, and 6,576,665. However, dosage forms of calcium acetate present a two-fold clinical dilemma, particularly for dialysis patients, who are a significant patient population that is treated with calcium acetate. On one hand, dialysis patients who may suffer from renal diseases such as end stage renal disease, find such solid dosage forms difficult to swallow due to their bulk size. The difficulty is exacerbated because such patients need to consume large dosages of calcium acetate, and consequently they must swallow many pills. Additionally, as mentioned above, such patients need to consume the pills prior to a meal. A third and equally undesirable characteristic of calcium acetate is that it has a repugnant bitter taste that is very unpleasant to the palate and is difficult to mask. Because solid dosage forms of calcium acetate must be able to disintegrate in the intestine, oral consumption of calcium acetate pills formulated to achieve this objective often leave particles of calcium acetate in patients' mouths, which particles leave the characteristic bad taste.
On the other hand, calcium acetate is water soluble, and liquid formulations of calcium acetate might be thought to alleviate the above-mentioned shortcomings of solid dosage forms of the drug. However, solutions of calcium acetate are many times more potently repugnant to the palate than are solid dosage forms. Additionally, it is very difficult to mask the taste of solubilized calcium acetate. Moreover, dialysis patients are restricted to limited fluid intake, and liquid dosage forms therefore could further complicate the patients' treatment regimens.
Consequently, despite the clear benefits of calcium acetate-based treatments, patients will typically fail to take the proper doses of their medicine, or they will turn to antacids as an alternative to these difficult-to-swallow unpalatable medications. The inventors are unaware of any liquid formulation of calcium acetate that could overcome the shortcomings of solid dosage forms while simultaneously addressing the above-mentioned hazards of liquid formulations. These considerations thus evidence a need in the art for liquid formulations of calcium acetate that mask the unpleasant taste, and yet are so limited in volume as to be efficacious in treating renal disease patients who are undergoing dialysis treatment.